The present invention relates to a vibratory roller for compacting a road surface and the like.
Compacting rollers are used for compacting an embankment of a road or a dam structure, or for compacting a road surface with asphalt paving. Generally, compacting rollers with steel wheels are classified, in terms of arrangement of the compacting wheels (hereinafter referred to as xe2x80x9crollsxe2x80x9d ), into a tandem type, in which front and rear rolls are arranged in line so that one rut is positioned on top of the other between the ruts of the front and rear rolls, and a macadam type, in which three rolls are employed. Further, a-vibration generating device may be provided on the compacting roller. The compacting roller with a vibration generating device enables to compact the road surface at high densities because it can compact the road surface while vibrating the rolls. The vibration generating device is applicable to both tandem type and macadam type rollers, and the compacting roller with the vibration generating device is known as a vibratory roller.
Of these compacting rollers, a macadam-type vibratory roller is disclosed in Japanese Utility Model Publication No. HEI.3-24647. FIG. 9 schematically shows an inner structure of the roll of the conventional macadam-type vibratory roller. As shown in FIG. 9, a stationary portion 53a of a roll-driving motor 53, which rotates a roll 52, is fixed to a side of a body 51, and an output portion 53b of the roll-driving motor 53 is fixed to the roll 52 through a bracket 54 and rubber vibration isolators 55. A reference numeral 56 indicates a vibration generating device. A casing of the vibration generating device 56 is fixed to the roll 52, and the vibration generating shaft (not shown) within the casing is connected to a vibrating motor 57. A stationary portion 57a of the vibrating motor 57 is fixed to a bracket 58, which extends from an upper part of the body 51 toward the outer surface of the roll 52 and further into the inner region of the roll 52.
In most cases, the macadam-type vibratory roller and the tandem-type vibratory roller are distinct in its usage. The tandem-type vibratory roller is used when widely and entirely compacting a road surface, such as an asphalt pavement, and the macadam-type vibratory roller is used when compacting and connecting a joint between newly constructed road surfaces or a joint between a newly constructed road surface and an existing road surface.
In a compaction work with the use of the tandem-type vibratory roller, the following drawbacks have been pointed out.
Normally, the tandem-type vibratory roller in 7 to 9 tons has a compacting width (or roll width) of about 1.5 to 1.7 meters. For example, when compacting one traffic lane of a roadway (viz. about 3.8 meter width), at least three compacting lanes are required. In order to reduce the number of compacting lanes, it is considered that the roll width may be increased. However, increasing the roll width would result in increased dragging of the road surface at the end of the roll positioned at the outer side of a curve, for example when compacting the curved road surface while turning the vibratory roller. This leads to deterioration in pavement quality. Such a problem can be overcome by dividing the roll into plural parts and providing a differential mechanism or differential gears. However, this is not preferable because the construction of the vibratory roller becomes complicated and the manufacturing cost thereof also increases.
In terms of drain, the roadway is usually paved to create a slight inclination from the centerline to both road ends, as illustrated in FIG. 8. When compacting such a roadway by the tandem-type vibratory roller along the centerline, the contacting characteristics of the roll 61 becomes worse at its ends due to the width of the roll 61. This is shown in FIG. 8A. As a result, there would be an irregularity in compaction between the road surface compacted by the center part of the roll 61 and the road surface compacted by the end parts of the roll 61.
Generally, as the roll diameter becomes greater, the contacting characteristics against the road surface may be improved and smoother finishing of the road surface can be achieved. However, in the tandem-type vibratory roller, increasing the diameter of the roll would arise other drawbacks, such as deteriorated visibility from the driver""s seat and increased size of the body.
In the tandem-type vibratory roller, a supporting member, such as a yoke, is positioned outwardly of the end surface of the roll. For this reason, when compacting the road surface in close proximity to a wall of the structure, the operator cannot move the roll in the immediate proximity position toward the wall because of a projection amount of the supporting member (side overhang), and so non-compacting parts remain on the road surface. In this event, a further operation is required to compact the non-compacting parts, and compacting equipment such as a tamper is conventionally used for this purpose.
In order to eliminate the above drawbacks, if the macadam-type vibratory roller is used, instead of the tandem-type vibratory roller, for entirely compacting the road surface, it may be advantageous in the following reasons.
With regard to the problem (1) relating with compacting width, the macadam-type vibratory roller has a constitution such that either front or rear rolls are positioned in pair at both sides of the body, and a differential mechanism is already provided or a differential mechanism is readily mounted. Therefore, dragging of the road surface hardly occurs during the compaction on the curved road surface, even if the compacting width (viz. the total width of the three rolls except for the superposed roll width) is increased. The compacting width of the 9 to 12 ton class macadam-type vibratory roller is generally about 2.1 meters, and when compacting the aforementioned lane (about 3.8 meter width) of the roadway, only two compacting lanes are required.
With regard to the problem (2) relating with contacting characteristics, it is preferable when compacting the road surface with a slight inclination by the macadam-type vibratory roller as illustrated in FIG. 8B than when compacting by the tandem-type vibratory roller as illustrated in FIG. 8A, because the width of each roll 52 is smaller, which leads to excellent contacting characteristics against the road surface. The finishing quality of the road surface is therefore uniform, and in other words, there are few differences in the road surface qualities due to compaction at different parts of the roll.
Further, with regard to the problem (3) relating with roll diameter, the macadam-type vibratory roller does not suffer from deteriorated visibility from the driver""s seat or increased size of the body, because a pair of rolls 52 is supported at both sides of the body 51 and thus increasing the roll diameter does not affect the body 51 positioned intermediate between the rolls 52.
As mentioned above, various remarkable effects can be expected when compacting the road surface with the use of the macadam-type vibratory roller. However, when compacting the road surface widely and effectively, the whole rolls including the pair of right and left rolls 52 have to be vibrated simultaneously. In the conventional macadam-type vibratory roller, it is difficult to vibrate the right and left rolls 52 simultaneously by the following reasons.
As shown in FIG. 9, the macadam-type vibratory roller comprises a pair of rolls 52 axially supported at both sides of the body 51. Since the width of each roll 52 is considerably small in comparison with that of the roll of the tandem-type vibratory roller, on one hand, it is effective for the aforementioned problems (1) and (2). On the other hand, depending on road surface conditions, a small width roll 52 is liable to occur rocking vibration (viz. vibration rocking in right and left directions) at the roll 52 as illustrated by arrows in FIG. 9. The rocking vibration becomes greater as the ratio of the roll width to the roll diameter is small. The rocking vibration hardly occurs if the roll width is considerably large, such as in the case of the tandem-type vibratory roller. However, in the macadam-type vibratory roller where the roll width is small and the rolls 52 are supported in a cantilevered fashion to the body 51, the rocking vibration is enhanced if the center of gravity of the roll does not correspond with the center of vibration.
Accordingly, in the conventional macadam-type vibratory roller, when vibrating the pair of right and left rolls 52 simultaneously, vibration derived from the rocking vibration is transmitted from both sides of the body 51 regardless of the provision of rubber vibration isolators 55. As a result, such a heavy vibration is transmitted to the driver""s seat that the operator cannot sit on the seat, and also irregularly paved parts are made on the road surface when compacting with the macadam-type vibratory roller. For this reason, the conventional macadam-type vibratory roller is mainly used for compacting the road surface in a particular and localized area, such as compacting and connecting a joint on the road surface, with one of the right and left rolls 52 vibrating.
In the conventional macadam-type vibratory roller, there is also a drawback that the deflection side of the rubber vibration isolator 55 varies because the isolator 55 rotates together with the roll 52, and thereby suspended load becomes alternate load.
Further, likewise the tandem-type vibratory roller, the conventional macadam-type vibratory roller has a problem (4) relating with side overhang. In other words, as shown in FIG. 9, because the bracket 58 projects outward from the roll 52, the operator cannot move the roll 52 in the immediate proximity position toward the wall of the structure, and non-compacting parts remain on the road surface.
With the foregoing drawbacks of the prior art in view, the subject of the present invention is to provide a vibratory roller having a pair of rolls supported in a cantilevered fashion to the body, which vibratory roller allows a compaction work with both rolls vibrating simultaneously.
According to a first aspect of the invention, there is provided a vibratory roller comprising: a pair of rolls axially supported at both sides of a body in a cantilevered fashion; a pair of vibration generating devices for vibrating each of the rolls; a pair of vibrating motors for driving each of the vibration generating devices; and a pair of roll-driving motors for rotating each of the rolls, wherein the rolls are connected to each other through the roll-driving motors and by a connecting member, and the connecting member is attached to the body through vibration isolating members.
With such a constitution, because the rolls are connected to each other through the roll-driving motors and by the connecting member, and further the connecting member is attached to the body through vibration isolating members, occurrence of the rocking vibration is prevented and the compacting operation can be carried out with both right and left rolls vibrating simultaneously. Therefore, if the rear roll vibrates i n addition to the front pair of rolls, an effective and high density compaction can be achieved in a wide range road surface.
According to a second aspect of the invention, the vibration isolating members are arranged outside of the body.
With such a constitution, because the vibration isolating members are arranged outside of the body, sufficient free layout space for the driving engine or the hydraulic piping can be made.
According to a third aspect of the invention, each of the roll-driving motors is a hollow construction-type motor with a through opening, and the roll-driving motor is positioned between the vibrating motor adjacent to the body and the vibration generating device adjacent to the roll. And a driving member for driving the vibration generating device is inserted through the through opening and is connected to the vibrating motor.
With such a constitution, because the side overhang is overcome, the operator can move the roll in the immediate proximity position toward the wall of the structure. Therefore, the compacting operation is carried out effectively and uniform finishing quality of the paved road surface is achieved.